Recurrence Patterns after Radiotherapy for Glioblastoma with [(11)C]methionine Positron Emission Tomography-Guided Irradiation for Target Volume Optimization.

11C methionine (11C-MET) is increasingly being used in addition to contrast-enhanced MRI to plan for radiotherapy of patients with glioblastomas. This study aimed to assess the recurrence pattern quantitatively. Glioblastoma patients undergoing 11C-MET PET examination before primary radiotherapy from 2018 to 2023 were included in the analysis. A clinical target volume was manually created and fused with MRI-based gross tumor volumes and MET PET-based biological target volume. The recurrence was noted as an area of contrast enhancement on the first MRI scan, which showed progression. The recurrent tumor was identified on the radiological MR images in terms of recurrent tumor volume, and recurrences were classified as central, in-field, marginal, or ex-field tumors. We then compared the MET-PET-defined biological target volume with the MRI-defined recurrent tumor volume regarding spatial overlap (the Dice coefficient) and the Hausdorff distance. Most recurrences occurred locally within the primary tumor area (64.8%). The mean Hausdorff distance was 39.4 mm (SD 32.25), and the mean Dice coefficient was 0.30 (SD 0.22). In patients with glioblastoma, the analysis of the recurrence pattern has been mainly based on FET-PET. Our study confirms that the recurrence pattern after gross tumor volume-based treatment contoured by MET-PET is consistent with the FET-PET-based treatment described in the literature.

Stereotactic body radiotherapy in lung cancer: a contemporary review.

The treatment of early stage non-small cell lung cancer (NSCLC) has improved enormously in the last two decades. Although surgery is not the only choice, lobectomy is still the gold standard treatment type for operable patients. For inoperable patients stereotactic body radiotherapy (SBRT) should be offered, reaching very high local control and overall survival rates. With SBRT we can precisely irradiate small, well-defined lesions with high doses. To select the appropriate fractionation schedule it is important to determine the size, localization and extent of the lung tumor. The introduction of novel and further developed planning (contouring guidelines, diagnostic image application, planning systems) and delivery techniques (motion management, image guided radiotherapy) led to lower rates of side effects and more conformal target volume coverage. The purpose of this study is to summarize the current developments, randomised studies, guidelines about lung SBRT, with emphasis on the possibility of increasing local control and overall rates in "fit," operable patients as well, so SBRT would be eligible in place of surgery.

LINAC-based SBRT in treating early-stage NSCLC patients-single institution experience and survival data analysis.

Aim: This single institute prospective study aimed to evaluate the feasibility of LINAC-based stereotactic body radiotherapy (SBRT) in treating patients with early-stage non-small cell lung cancer (NSLSC). We focused on the survival data with the local and distant control profiles and the cancer- and non-cancer-specific survival. Treatment-related side effects were also collected and analyzed. Methods: Patients with early-stage NSCLC between January 2018 and October 2021 were included in our prospective study; a total of 77 patients receiving LINAC-based SBRT were analyzed. All patients had pretreatment multidisciplinary tumor board decisions on SBRT. The average patient age was 68.8 years (median: 70 years, range: 52-82); 70 patients were in ECOG 0 status (91%), while seven patients were in ECOG 1-2 status (9%). 52% of the patients (40) had histologically verified NSCLC, and the other 48% were verified based on PETCT results. We applied the SBRT scheme 8 x 7.5 Gy for central tumors (74%) or 4 x 12 Gy for peripheral tumors (26%). Results: The mean follow-up time was 25.4 months (median 23, range 18-50). The Kaplan-Meier estimation for overall survival in patients receiving LINAC-based SBRT was 41.67 months. Of the 77 patients treated by SBRT, death was reported for 17 patients (9 cases cancer-specific, 8 cases non-cancer specific reason). The mean local tumor control was 34.25 months (range 8.4-41), and the mean systemic control was 24.24 months (range 7-25). During the treatments, no Grade I-II were reported; in 30 cases, Grade I non-symptomatic treatment-related lung fibrosis and two asymptomatic rib fractures were reported. Conclusion: In the treatment of early-stage NSCLC, LINAC-based SBRT can be a feasible alternative to surgery. Although we reported worse OS data in our patient cohort compared to the literature, the higher older average age and the initial worse general condition (ECOG1-2) in our patient cohort appear to be the reason for this difference. With the comparable local control and survival data and the favorable side effect profile, SBRT might be preferable over surgery in selected cases.

Plan Quality Assessment of Fractionated Stereotactic Radiotherapy Treatment Plans in Patients With Brain Metastases.

Background and Purpose: The treatment options available in the management of brain metastases includes fractionated stereotactic radiotherapy (FSRT) and stereotactic radiosurgery (SRS) treatments. FSRT treatments have proved to be useful mainly in the treatment of larger volumes. This study aims to evaluate the FSRT treatment technique used in our department based on various plan quality indices. Methods and Materials: 24 treatment plans of 23 patients were analyzed. Volumetric modulated arc therapy (VMAT) plans were generated in line with the department protocol. The following parameters were extracted: Radiation Therapy Oncology Group conformity index (RTOG CI), Paddick conformity index (Paddick CI), gradient index (GI), quality index (Q), homogeneity index (HI), and V24.4 volume as a parallel index of V12 used at SRS plan evaluation. Results: Plan conformity was acceptable, RTOG CI mean was 0.942; Paddick CI mean was 0.824. The mean GI value was 6.146. The mean of HI and Q indices were 1.263 and 0.94, respectively. V24.4 mean was 33.434 cm3. All plans achieved clinically acceptable organs-at-risk (OAR) constraints. PTV volumes were clustered into either 10 cm3 or 15 cm3 bins depending on the plan quality metric we used. The mean values show a balanced distribution of plan indices along the various PTV bins. Discussion: Our results based on the derived indices show that our FSRT approach can achieve clinically acceptable treatment plans. Furthermore, the clustering of PTV volumes show that these plan quality metrics remain acceptable for a wide spectrum of PTV volumes.

CBCT Verification of SRT for Patients With Brain Metastases.

BACKGROUND: The aim of our work is to demonstrate the role of image guidance and volumetric imaging in stereotactic radiotherapy (SRT) of brain metastases. METHODS: Between 2018 and 2020, 106 patients underwent intracranial stereotactic radiotherapy. 10 patients with metastatic brain tumors treated with SRT were randomly selected and included in our study model. Patients were scanned pre- and post-treatment with cone beam CT. Total of 100 verifications of 50 stereotaxic treatments were performed and analyzed. RESULTS: Population mean X, Y, Z values were -0.13 cm, -0.04 cm, -0.03 cm, respectively, rotation values 0.81°, 0.51°, 0.46°, respectively. Systematic error components for translational displacements pre corrections were as follows: 0.14 cm for X, 0.13 cm for Y and 0.1 cm for Z. Systematic error components of the post-treatment HR 3D CBCTs were as follows: 0.01 cm for X, 0.06 cm for Y and 0.04 cm for Z. CONCLUSIONS: Population mean values close to 0 confirmed that there is no systematic variation in our system and the accuracy of our equipment and tools is reliable. HR 3D CBCT scans performed pre SRTs further refine patient and target volume setting, support medical decision making and eliminate the possibility of gross error.